This invention generally relates to a radar system and more particularly, to improvements in an airborne monopulse radar system used for tracking ground targets.
In the use of conventional prior art monopulse radar systems for tracking ground targets, reliance is generally placed on beam patterns in the sum and difference channels to accurately position or align the antenna to point towards a preselected target. The beam patterns represent received energy which has been reflected by the preselected target. In general, such a target tracking technique has utility only when high target tracking accuracy is not required and/or if the reflected energy vs. noise from the target, i.e., the signal-to-noise ratio, is high. Extreme difficulties arise where the selected target to be tracked has a weak return signal in that the noise in the system, including thermal noise, may nearly obliterate the weak signals from the target thereby making accurate tracking nearly impossible. In order to counteract the effect of the noise, energy reflected from a larger area around the ground target may be accepted to improve the signal-to-noise ratio. However, in that there are wide variations in the back-scatter amplitude relative to azimuth angle, the angle information will be deteriorated and accurate target azimuth angle pointing usually remains nearly impossible. Thus, most airborne monopulse radar systems used for tracking ground targets are limited in their utility by the need for high tracking accuracy and the usual weak return signals produced by ground targets. As such, it is clear that a need exists for improvement in monopulse type radar systems intended to be used in the airborne tracking of ground targets.